FullDuplexSerial at 5bps

mojorizing

Is there any reason why the FullDuplexSerial.spin at obex.parallax.com/objects/54/ won't work at 5 bps? Seems like it should work at any odd baud rate....

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Phil Pilgrim (PhiPi)

Looking at the code for FullDuplexSerial, there's no apparent reason for it not to work at 5 baud. Are you sure the baudrate is the source of your trouble and not something else? Can you show us your program?

-Phil

mojorizing

Hi Phil,

This is using a USB Pro Dev. brd. The usual debug using pin 31 and 30 to output what's coming into pin 1, so the prop. is a simple pass thru to a PC running Parallax Serial Term.

CON
   
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000
 
VAR
      BYTE            Data


OBJ

  ComputerConnection : "Debug_PC2"         'data connection to the PC
  HammerConnection :   "FullDuplexSerialPlus"  'data connection to the Hammer

PUB Main

  HammerConnection.start(1, 2, 0, 5)  ' pin1 to recv - only to monitor traffic, pin2 not used. Need to change buad rate for diff. ECU.

  ComputerConnection.start(57600)
  waitcnt(clkfreq*2 + cnt)
  ComputerConnection.putc(ComputerConnection#FF)  'Form Feed
  
  Repeat
    CommunicateFromHammer
    UpdateVariables
    
PUB CommunicateFromHammer
  ' monitor data from Hammer
  
  Data := HammerConnection.GetHex
  
PUB UpdateVariables


     ComputerConnection.Str(String(ComputerConnection#TAB))
     ComputerConnection.hex(Data,2)
     ComputerConnection.Str(String(ComputerConnection#CR))

Using another computer serially connected to the Pro Brd DB9 connection, all's well with 300, 600 etc. baud. I know of no terminal program that you can dial down to 5 baud (not my favorite RealTerm either) to check, but on my o'scope the 5 baud input looks as it should. I own a copy of Viewport, so I'll fire that up. Can you see anything amiss?

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Phil Pilgrim (PhiPi)

You're calling GetHex, which requires the sending device to send hex data as a zero-terminated string. Is this what your "hammer" device does?

-Phil

hinv

Can I ask why 5baud? Are you doing some long distance low power communication?

mojorizing

This project is an OBD code reader on a vehicle (porsche 911 made from '89 to '94) that uses ISO:9141:1989 protocol.
A certain initial 5bps address byte is sent on the "L" line to a certain control unit in the car.

Phil, you're correct, and this explains it....this isn't sent using a zero terminated string.

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